Term: atrium anatomical region
Name: atrium
Synonyms:
Definition: Cavitated compound organ that receives inflow of deoxygenated blood and delivers it to a muscular cardiac ventricle. Valves are present to direct flow. There are only two chambers present in the fish heart.
Ontology: Anatomy Ontology [ZFA:0000471]

Name: anatomical region
Synonyms:
Definition: A 3D region in space without well-defined compartmental boundaries; for example, the dorsal region of an ectoderm.
Ontology: Spatial Ontology [BSPO:0000070]